As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased. Among such secondary batteries is a lithium secondary battery having high energy density and operating voltage and excellent preservation and service-life characteristics, which has been widely used as an energy source for various electronic products as well as for the mobile devices.
Based on their external and internal structures, secondary batteries are generally classified into a cylindrical battery, a prismatic battery, and a pouch-shaped battery. Especially, the prismatic battery and the pouch-shaped battery, which can be stacked with high integration and have a small width to length ratio, have attracted considerable attention.
Also, the secondary batteries have attracted considerable attention as an energy source for electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles, which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel. As a result, the secondary batteries are being applied to an increasing number of applications owing to advantages thereof, and, in the future, the secondary batteries are expected to be applied to even more applications and products.
As applications and products, to which the secondary batteries are applicable, are increased, kinds of batteries are also increased such that the batteries can provide powers and capacities corresponding to the various applications and products. Furthermore, there is a strong need to reduce the size and weight of the batteries applied to the corresponding applications and products.
For example, small-sized mobile devices, such as mobile phones, personal digital assistants (PDA), digital cameras, and laptop computers, use one or several small-sized, lightweight battery cells for each device according to the reduction in size and weight of the corresponding products. On the other hand, middle- or large-sized devices, such as electric bicycles, electric motorcycles, electric vehicles, and hybrid electric vehicles, use a middle- or large-sized battery module (which may also be referred to as a “battery pack”) having a plurality of battery cells electrically connected with each other because high power and large capacity is necessary for the middle- or large-sized devices. The size and weight of the battery module is directly related to an accommodation space and power of the corresponding middle- or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, lightweight battery modules.
Meanwhile, when battery cells are connected to one another, in a state in which the battery cells are stacked, so as to increase the capacities of battery modules, the dissipation of heat from the battery cells becomes serious. For lithium secondary batteries, heat is generated from the lithium secondary batteries during the charge and discharge of the lithium secondary batteries. If the heat is not effectively removed from the lithium secondary batteries, the heat accumulates in the respective lithium secondary batteries, resulting in the deterioration of the lithium secondary batteries, and the safety of the lithium secondary batteries is greatly lowered. In particular, for a battery requiring high-speed charging and discharging characteristics as in a power source for electric vehicles and hybrid electric vehicles, a large amount of heat is generated from the battery when the battery instantaneously provides high power.
Also, a water cooling type cooling structure or an air cooling type cooling structure, which is widely used as a cooling structure for cooling such a battery module, is generally fixed to the battery module. As a result, it is difficult to apply various cooling structures to the battery module as needed.
In connection with this matter, for example, Japanese Patent Application Publication No. 2004-031281 discloses a cooling structure of an electrode stacked type battery configured in a structure in which a pair of laminate films each including a metal layer and a resin layer are disposed at opposite sides of an electrode assembly manufactured by stacking a cathode and an anode in a state in which a separator is disposed between the cathode and the anode, and edges of the laminate films are fixed to each other in a tight contact manner, wherein a pair of pushing members push opposite sides of the electrode stacked type battery, the pushing members protrude more outward than the outer circumference of the electrode stacked type battery, the protruding regions of the pushing members function as heat dissipation members which dissipate heat generated from the electrode stacked type battery.
However, the above-mentioned technology has problems in that it is necessary to manufacture a battery cell case in a complicated structure and mount the manufactured battery cell case into a battery, which is troublesome. Also, the above-mentioned technology is limited to a structure in which an air cooling type cooling fin is applied upon stacking of batteries to manufacture a battery module, with the result that it is difficult to use various heat dissipation members, such as a water cooling type cooling plate or a non plate-shaped cooling member.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above-mentioned problems.